Flexible module interconnect system

ABSTRACT

A flexible modular interconnect system is provided which utilizes a backplane having a plurality of module receiving slots and a plurality of circuit modules, selected ones of the circuit modules being mounted in at least selected ones of the slots. The modules may be of a variety of different types. First and second switches are provided for each circuit module with selected lines from module logic being connected to each of the switches. The first and second switches for each module are interconnected and the first switch for the selected modules are connected to the second switch for adjacent modules. Selected information concerning each module is provided to each adjacent module and control logic is provided which is responsive at least in part to the received information concerning the adjacent module for controlling the state of an appropriate switch. The switches may also be controlled from an external source. By selectively controlling the state of the switches, the modules may be flexibly interconnected.

BACKGROUND OF THE INVENTION

This invention relates to modular electronic equipment having themodules mounted to a backplane and more particularly to such a systemwhich permits the modules to be flexibly interconnected withoutrequiring rewiring of the backplane.

FIELD OF THE INVENTION

Many types of electronic equipment are designed to have a plurality ofcircuit modules, such as printed circuit boards, plugged into a prewiredbackplane or mother board. The backplane may for example be wired sothat all of the modules are connected to a single system bus, the wiringmay interconnect the modules in daisy chain fashion, or the modules maybe interconnected in some other predetermined configuration.

A backplane system such as that described above works well so long asthe equipment is being used to perform only a single function, and onlya single type of module is being used. However, there are applicationswhere it may be desired to utilize the same equipment or system indifferent modes or configuration or to perform different functions. Forexample, a basic piece of equipment may be designed to operate with anumber of different computer systems and may require slightly differentmodules or different interconnections of modules depending on thecomputer system with which it is interfaced. Similarly, it may bedesirable to interface a particular type of equipment to a number ofdifferent communications protocols (i.e., Ethernet, token passing, etc.)which may require slight variations in modules or interconnections.

While some flexible backplane systems exist, these systems have onlylimited flexibility, and in particular have been limited to a particulartype of interconnection between modules. Thus, while such a system mightpermit the length of the bus in a system to be varied, it does notpermit the system to be reconfigured from a bus to a daisy chainconfiguration, to a loop back mode or the like.

Another limitation with existing flexible systems is that they respondonly to the particular module or modules inserted in the system and thusare capable of operating in only a single mode for a given combinationof modules. This further limits the flexibility in use of such systems.

Thus, a need exists for an improved flexible modular backplaneinterconnect system which permits far greater flexibility in the mannerin which modules may be connected or interconnected and in the moduleswhich may be used in the system, while still remaining relatively simpleand inexpensive.

SUMMARY OF THE INVENTION

A flexible modular interconnect system is provided which utilizes abackplane having a plurality of module receiving slots and a pluralityof circuit modules, selected ones of the circuit modules being mountedin at least selected ones of the slots. Each of the modules has apredetermined module logic which may vary from module to module so thatthe modules may be of one or more different types. A first and a secondswitch means are provided for each circuit module, each of which switchmeans is settable to at least two different states. For one embodimentof the invention, the switch means have a plurality of switch elementswhich are independently settable. Selected lines from each module logicare connected to the first switch means for the module and otherselected lines from the module logic are connected to the second switchmeans for the module. The first and second switch means for a module arealso interconnected and the first switch means for selected modules areconnected to second switch means for adjacent modules. Selectedinformation concerning each module is provided to each adjacent moduleand a control means is provided which is responsive at least in part tothe received information concerning the adjacent modules for controllingthe state of the switch means for a module which switch means isconnected to such adjacent module. The state of the switch meanscontrols the interconnections for the module logic lines connectedthereto. Thus, by selectively controlling the state of the switch means,the modules may be flexibly interconnected. In addition to beingresponsive to information concerning adjacent modules, the control meansmay also operate in response to external controls, such as manual inputsfrom the user or control signals obtained from an external processor orother control device, further enhancing the flexibility of the system.While the switch means and the control means may be mounted on thebackplane, the flexibility of the system is enhanced by having theseelements mounted on each module. Each module receiving slot may have aplurality of first contacts and a plurality of second contacts, some ofthe first and second contacts being connected to the control means andthe remaining first and second contacts being connected respectively tothe first and second switch means.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention as illustrated inthe accompanying drawings.

IN THE DRAWINGS

FIG. 1 is a diagram illustrating three adjacent module receiving slotsin a backplane in accordance with the teachings of this invention.

FIG. 2 is a schematic diagram illustrating a single module in accordancewith the teachings of this invention connected in a looped back mode.

FIG. 3 is a schematic diagram illustrating two adjacent modulesconnected in a daisy chain mode which terminates at the B module.

FIG. 4 is a partial schematic diagram of a single module connected inthe attached bus mode.

FIG. 5 is a schematic diagram of a single module connected in the bypassmode.

FIG. 6 is schematic diagram of a single module for an alternativeembodiment of the invention wherein part of the module is connected inthe daisy chain mode and part in the looped back mode.

DETAILED DESCRIPTION

Referring first to FIG. 1, and in accordance with this invention, abackplane 10 is provided having a plurality of module receiving slots 12formed therein. Each slot 12 has a plurality of pins 14 which pins aredivided into a left group of pins and a right group of pins. For thepreferred embodiment there are a total of thirty-two pins for each slotwith sixteen of the pins being left pins and sixteen of the pins beingright pins. The right pin of each slot is connected to the correspondingleft pin of the adjacent slot by a line 16. Thus, right pin number 1 ofslot 12A is connected to left pin number 1 of slot 12B, right pin number2 of slot 12A is connected to left pin number 2 of slot 12B, etc. Thefirst two of the lines 16 interconnecting each pair of slots 12 containtype code information for the module in the left one of the twointerconnected slots. Similarly, the third and fourth linesinterconnecting each two adjacent slots contain a coded indication ofmodule type for the module in the right one of the two slots, Thus, inFIG. 1, the first two lines interconnecting slots 12A and 12B wouldcontain two bit coded information concerning module type for the modulein slot A, while the third and fourth lines would contain coded moduletype information for the module in slot 12B. If more than four moduletypes are employed, a greater number of lines can be allocated for thisfunction. Alternatively, the same two or more lines may be time sharedto pass coded information concerning both modules, or the module typecode may be serially transmitted from each module over a single line.Different module types could, for example, be utilized to interface thesystem to different computers or for use with different communicationprotocols. The remaining twelve lines interconnecting each pair ofadjacent slots contain data, programming, or other information to bepassed between or through the interconnected modules.

While only three slots are shown in FIG. 1, it is apparent that, formost electronic devices, there would be a much larger number of modulereceiving slots on backplane 10 and that these slots do not necessarilyneed to be arranged in a single row as shown in FIG. 1, but could bearranged in a matrix or in any other desired configuration.

FIG. 2 illustrates the elements on a single module for a preferredembodiment. Referring to this figure, the module includes module logic20, an interface left logic switch 22, an interface right logic switch24, and control logic 26. Module logic 20 may be and circuitry,including hardware and/or software, usable on an electronic circuitmodule and the exact nature of this logic and circuitry does not formpart of the present invention. Module logic 20 has a first group ofinput/output lines 28 which are connected as one input to left logicswitch 22 (i.e., to the C input thereof) and a second group ofinput/output lines 30 which are connected to the C input of right logicswitch 24. While the number of lines 28 and 30 may be equal, this is nota limitation on the invention. The B contact of the logic switches 22and 24 are interconnected by lines 32. There are also a plurality ofleft function input/output lines 34 connected to the A contact of leftlogic switch 22 and a plurality of input/output lines 36 connected tothe A contact of right logic switch 36. As will be discussed in greaterdetail later, switches 22 and 24 may be independently connected in anyof a variety of configurations, the configuration or state of switches22 and 24 at any given time being determined by control signals on lines38 and 40 respectively from control logic 26. The signals on lines 38and 40 may either be continuous to maintain the corresponding logicswitch in a desired state or, preferably, the switches are set to adesired state by a coded input on the corresponding lines 38 or 40 andremain in such state until a new control input is received.

Each interface logic switch may be a mechanically controlled switch suchas a relay, but is preferably an electronic switch of standardconfiguration formed utilizing, for example, three separate switchchips, e.g., DM74LS244 TriState sold by National Semiconductor Corp.,Santa Clara, Calif.

Control logic 26 may operate in response to two different types ofinputs. First, each control logic 26 receives type code inputs from themodule in the slot to the left thereof on lines 42In. Lines 42 are thefirst two of the lines 16 interconnecting each two adjacent module slots12 (FIG. 1). Control logic 26 also generates an output on lines 42Outwhich lines contain the type code of the module which is to be passed onto the control logic 26 of the next module to the right. Similarly, thecontrol logic 26 receives inputs on lines 44In which contain the typecode for the module in the slot 12 to the right thereof, and the controllogic generates a type code output on the lines 44Out, providing itstype code to the module to the left thereof. The code on lines 42Out and44Out should be the same code. Normally the inputs on lines 42In and/or44In will control the outputs on control lines 38 and 40 from thecontrol logic, and will thus determine the state for switches 22 and 24.Whether it is the input on 42In, the input on 44In, or a combination ofboth which determine the outputs on lines 38 and 40 will depend on thenature of the module itself and will vary with application.

In addition to the inputs on lines 42 and 44, it is also possible forcontrol logic 26 to receive an input on lines 46 from an externalcontrol device such as a microcomputer or other controller 48. Theinputs on lines 46 may also reflect a user generated input which may beapplied either directly from a user input device or through a controller48. Controller 48 may be a microcomputer or some form of dedicatedcontroller device associated with the particular system.

Control logic 26 may be special purpose logic which is hard wired toperform the specific logic function, may be a programmable logic arraywhich is programmed to perform the desired logic function, may be a ROMdecoder which, in response to a predetermined set of inputs on the lines42In, 44In and 46 generates predetermined outputs on lines 38 and 40, orcould be some other form of programmable logic device which generatespredetermined outputs in response to a predetermined combination ofinputs. While the function of control logic 26 is critical to theoperation of the invention, the exact logical function performed by thiscircuit will vary with module and application and the specifichardware/software used for this application do not form part of thepresent invention.

The setting of switches 22 and 24 determine the mode in which the moduleoperates. In FIG. 2, the circuit is shown connected in a "looped back"mode wherein information outputted on a line or lines 28 or 30 is fedback through the corresponding logic switch 22 or 24, lines 32 and theother logic switch and line back into the module 20. The module thusperforms an independent function and does not interact with othermodules in the system. Such a module may for example be a module whichdisplays a time varying value with the logic for generating anddisplaying such value being within module logic 20 for such module.

FIG. 3 shows a pair of modules 18A and 18B, each of which is in acorresponding slot 12A and 12B. Each of the modules is shown ascontaining module logic 20, a left switch 22, a right switch 24, and acontrol logic 26. An external control 48 is also shown for each module18; however, for some embodiments of the invention, a single externalcontrol may be utilized as the external control 48 for all of themodules 18. The two modules 18A and 18B are interconnected in the mannerpreviously described with the A contacts of right switch 24A for module18A being connected through function lines 16 to the contact or terminalA of left switch 22B for module B. Left switch 22A may also have its Acontacts connected to the right switch 24 of a next adjacent module 18through lines 34A leading therefrom. However, for reasons which will bediscussed shortly, the A contact of right switch 24B would probably notbe connected to another module.

Modules A and B are connected as part of a daisy chain configurationwhich chain ends at module 18B. Thus, information received over line 34Ais passed through the A contact of switch 22A to the C contact of thisswitch and through lines 28A to module logic 20A. The inputtedinformation, either as received or as modified by module 20A is thenapplied through lines 30A to the C contact of right switch 24A. Thiscontact is connected to the A contact of switch 24A which is connectedthrough lines 36A and interconnected lines 16 to lines 34B leading tothe A contacts of left switch 22B. This contact is connected to the Ccontact of the switch which passes the signal through lines 28B tomodule logic 20B. However, since right switch 24B is open (i.e., thereare no connections within this switch), information cannot be passedfrom module logic 20B on to a next right adjacent module. The daisychain therefore ends at module 18B. However, module logic 20B may sendinformation back through lines 28B, switch 22B, lines 34B, 16, 36A,switch 24A and lines 30A to module logic 20A. Module logic 20A may theneither elect to send information back through the same path to modulelogic 20B, to pass the information from module logic 20B throughunaltered to the next left module in the chain, to perform various logicfunctions on this input before passing it on to the next left module tomerely utilize the received input or to perform some other function withit. FIG. 3 thus illustrates a daisy chain mode of operation and alsoillustrates the fact that, while in most applications the left switch 22and the right switch 24 for a given module will be in the same state,this is not always the case.

FIGS. 4 and 5 illustrate two additional modes in which the modules ofthis invention may be connected or interconnected. In FIG. 4, theterminals A, B and C of each of the switches 22 and 24 areinterconnected so that, depending on the condition of the module logic,information received at a terminal A for one of the switches may eitherbypass the module logic 20, passing through the switches and through thelines 32 interconnecting the switches, may pass through the module logic20 without being applied to the lines 32 as for the daisy chainoperation described previously in conjunction with FIG. 3, or may doboth, with the information being applied to module logic 20 and alsopassing through lines 32 to the next module in the chain. An example ofthis type of operation might be a token ring system where, when a tokenis transmitted on the line, the token passes through lines 32 if thereis no message at module 20 to be transmitted, but is captured by themodule logic and not passed through lines 32 when the module logic has amessage to transmit. Having captured the token, the module logic thenputs a message through for example lines 30 and switch 24 to lines 36leading to the next module. The token is then put on the end of themessage. The next module in the chain passes the message down the chain,but might capture the token portion of the message if it has a messageto transmit. A module may also elect to receive a message if the messageis addressed to the module.

FIG. 5 illustrates the bypass mode wherein the particular module logicis not active in the circuit. For this mode, contacts A and B on each ofswitches 22 and 24 are interconnected causing information received ateither switch to be passed through the lines 32 and the other of theswitches to the next adjacent module.

In the discussion so far, it has been assumed that all of the linesconnected to a given switch are treated in the same fashion. However, asillustrated by FIG. 6, this is not a limitation on the invention.

Referring to FIG. 6, it is seen that the left interface logic switch 60has two parts 60A and 60B and the right interface logic switch has twoparts 62A and 62B. Some of the lines 28 from module logic 20 areconnected to switch logic 60A and some of the lines 28 are connected toswitch 60B. Similarly, some of the lines 30 from module logic 20 areconnected to switch 62A and some of these lines are connected to switch62B. Control lines 38 from control logic 26 are adapted to independentlycontrol switches 60A and 60B such that these switches may be connectedin different modes. Thus, as shown in the figure, switches 60A may forexample be connected in a daisy chain mode while switches 60B areconnected in a loop back mode. Control lines 40 are similarly adapted toindependently control switches 62A and 62B. Thus, portions of modulelogic 20 may operate in one mode, such as a loop mode back mode, whilethe remaining portions of this circuit are operated in a different mode,for example, a daisy chain mode. Obviously the two portions of thecircuit operating in different modes may communicate with each other inthe module logic itself. While two independently controllable switchelements are shown for each switch logic in FIG. 6, it is apparent thatthree or more such elements could be provided for one or more of theswitches for a given application.

Similarly, while all of the switch connections are shown as beingbidirectional in the figures, the direction of switch connection couldbe independently controlled for each connection so that, for example, inFIG. 3 signals could flow to the right through the daisy chain, but notto the left. It is also possible for all of the connections to bemonodirectional. Further, while for the preferred embodiments, switchsettings are determined at least in part by signals on lines 42 and 44from adjacent modules, this is not a limitation on the invention and itis possible that the switch control could be solely from the externalsource or that control could be achieved in some other way.

While in the discussion above, switches 22 and 24, and control logic 26have all been positioned on module 18, and this is preferable because ofthe enhanced flexibility it provides, with suitable modification, one ormore of these elements could be on the backplane 10 for each slot 12.Further, while various switch setting and modes of operation have beendiscussed above, it is to be understood that such examples are notexhaustive, and that other settings or combinations of settings arepossible to establish different system operating modes. In addition,while the invention has been shown above with respect to preferredembodiments, it is apparent that variations could be made in thespecific logic components used and in their interconnection while stillretaining the desired flexibility. Thus, while the invention has beenparticularly shown and described above with respect to preferredembodiments, the foregoing and other changes in form and detail may bemade therein by one skilled in the art without departing from the spiritand the scope of the invention.

What is claimed is:
 1. A module interconnect system comprising:abackplane having a plurality of module-receiving slots; a plurality ofmodules mounted in selected ones of said slots and electricallyconnected to said backplane, each of said modules including a modulecircuit with input/output lines; a first switch means for each modulehaving a first group of said input/output lines connected thereto and asecond switch means for each module having a second group of saidinput/output lines connected thereto, each of said switch means havingat least two states; switch connection means for interconnecting thefirst and second switch means for each module; a first module connectionmeans for connecting the first switch means of a selected module to afirst adjacent module; a second module connection means for connectingthe second switch means of the selected module to a second adjacentmodule; and control means responsive to a control signal from anexternal source for controlling the state of the first switch means ofeach module to thereby selectably connect said first group ofinput/output lines, said second switch means and said first adjacentmodule; and for controlling the state of the second switch means of eachmodule to thereby selectably connect said second group of input/outputlines, said first switch means and said second adjacent module, saidcontrol signal including information representative of the module typeof said first and second adjacent modules.
 2. A module interconnectsystem as defined in claim 1 wherein said first and second switch meansfor each module are part of said module.
 3. A module interconnect systemas defined in claim 2 wherein said control means for each module is partof said module.
 4. A module interconnect system as defined in claim 2wherein each module-receiving slot includes a first and a secondplurality of contacts, at least some of the first and second contactsbeing connected respectively to the first and second switch means forthe module.
 5. A module interconnect system as defined in claim 3wherein said control signal is provided from an external source.
 6. Amodule interconnect system as defined in claim 1 wherein at least one ofsaid switch means includes first and second independently settableswitch elements, said first switch element having a first set of linesconnected thereto and said second switch element having a second set oflines connected thereto, said control means being operative toindependently control the first and second sets of lines.
 7. A moduleinterconnect system as defined in claim 1 wherein the first group ofsaid input/output lines is selectably connected by said first switchmeans to said first adjacent module.
 8. A module interconnect system asdefined in claim 1 wherein the first group of said input/output lines isselectably connected by said first switch means to said second switchmeans.
 9. A module interconnect system as defined in claim 1 whereinsaid first adjacent module is selectably connected by said first switchmeans to said second switch means.
 10. A module interconnect system asdefined in claim 1 wherein the first group of said input/output lines isselectably connected to said first adjacent module and to said secondswitch means.
 11. A module interconnect system as defined in claim 1wherein said first and second switch means for each module are part ofsaid module and wherein said first and second module connection meansinclude connection lines that extend from said first and second switchmeans, respectively, to said backplane.
 12. A module interconnect systemas defined in claim 1 wherein the first module connection means connectsthe first switch means of the selected module to the second switch meansof the first adjacent module.
 13. A module interconnect system asdefined in claim 12 wherein the second module connection means connectsthe second switch means of the selected module to the first switch meansof the second adjacent module.
 14. A module interconnect systemcomprising:a backplane having a plurality of module-receiving slots; aplurality of modules mounted in selected ones of said slots andelectrically connected to said backplane, each of said modules includinga module circuit with input/output lines; a first switch means for eachmodule having a first group of said input/output lines connected theretoand a second switch means for each module having a second group of saidinput/output lines connected thereto, each of said switch means havingat least two states; switch connection means for interconnecting thefirst and second switch means for each module; a first module connectionmeans for connecting the first switch means of a selected module to afirst adjacent module; a second module connection means for connectingthe second switch means of the selected module to a second adjacentmodule; control means responsive to a control signal for controlling thestate of the first switch means of each module to thereby selectablyconnect said first group of input/output lines, said second switch meansand said first adjacent module; and for controlling the state of thesecond switch means of each module to thereby selectably connect saidsecond group of input/output lines, said first switch means and saidsecond adjacent module; and means for providing selected informationconcerning each module to each adjacent module, said control means beingresponsive to said selected information concerning an adjacent modulefor controlling the state of the switch means for the module, saidmodules including at least two different types and said selectedinformation concerning each module including information concerning themodule type.